Alternative Energy Demystified, 2nd edition

Stan Gibilisco

Explanations for Quiz Answers in Chapter 7

1. We can't expect methane to deliver better engine performance than gasoline or diesel fuel (in terms of efficiency in converting the potential energy in the fuel to useful mechanical energy for propulsion). In fact, methane-fueled engines generally have lower performance ratings than conventional gasoline or diesel-fueled engines. Methane does lend itself to small-scale production. Methane combustion produces less carbon dioxide than gasoline combustion, and far less smoke than diesel-fuel combustion. The correct choice is B.

2. Flex-fuel engines not only work best for burning various gasoline/ethanol blends, but they're a requirement. Any engine designed for a specific fuel type (diesel, biodiesel, gasoline, ethanol, methane, or propane) can't be expected to work well with gasoline/ethanol blends ranging all the way from E10 to E85. The correct choice is B.

3. If we want to go strictly "by the book," we define the gasoline-gallon equivalent (GGE) of an alternative liquid fuel as the number of gallons of the alternative fuel necessary to produce the same number of British thermal units (Btus) as one U.S. gallon of gasoline. But we don't have to use the U.S. gallon or the British thermal unit. We only have to use the same units for both fuels being compared. For example, we can use liters and joules to calculate the GGE, and as long we use as these units to define the energy per unit volume of both gasoline and the alternative liquid fuel, the resulting GGE figure will turn out correct. The answer is C.

4. Most modern vehicles can burn gasoline containing up to 10 percent added ethanol with no adverse effects. If the percentage of ethanol gets higher, the engine must undergo specific modifications to allow for the difference in fuel combustion characteristics. Otherwise, the fuel will not burn efficiently, and some engine components might sustain damage. The correct choice is D.

5. Biodiesel is less likely than petroleum diesel to spontaneously catch on fire when transported, so the correct choice is C. Biodiesel can congeal, just as petroleum diesel can, if the temperature gets too low, so choice A is wrong. Neither biodiesel nor petroleum diesel are compressed for transport, so choice B is wrong. We can rule out choice D, of course, because the premise of the question is indeed correct. Once again, the answer is C.

6. Plant matter is a renewable resource, so choice A is obviously wrong. Plant-based fuels are no more susceptible to spontaneous combustion than other types of fuel in general, so choice C is wrong. Plant-based fuels are no more difficult to transport than other fuel types in general, so D is also wrong. The only choice remaining is B. Some people have indeed expressed concern that using plant matter to produce fuel takes away from its possible use as food for hungry people around the world. This argument applies especially to corn and wheat, which constitute vital components of many people's diets. Once again, the answer is B.

7. Ethanol motor-vehicle fuel derives largely from the processing of plant matter, particularly corn (in the United States), sugar cane (in Brazil), and wheat (in Canada). The correct choice is A.

8. Biodiesel motor-vehicle fuel can be obtained by processing used cooking oil, which would otherwise end up as waste matter. The correct choice is D.

9. Propane has a GGE of about 1.35, meaning that it takes roughly 1.35 times as much propane as gasoline to propel a vehicle of a given weight over a given distance. Stated another way, and in more specific terms, we can expect to get 1.35 times the operating range in a vehicle of a given weight on 16 gallons of gasoline, compared with 16 gallons of propane. The correct choice is B.

10. Biomethane derives from plant matter, rather than from "fossil fuel type" sources within the earth. (The key here lies in the prefix bio, which stands for for the word biological.) Composting works well for biomethane (biological methane) production. The answer is A.